Ecological Impact of Enhance Solar Ultraviolet Radiation on Phytoplankton at High Latitudes in the Arctic

[907692] holm - hansen最近的数据显示，在春季（3 - 5月）期间，北半球平流层的臭氧浓度每年都在下降，延续了过去十年记录的下降趋势。大气臭氧损耗的幅度在北极的高纬度地区最大，在低纬度地区逐渐减少。臭氧层这一保护层的损耗导致UV- b辐射（280-320 nm）增强，随着臭氧的逐渐损耗，入射到地球上的这些较短UV波长的影响呈指数级增加。由于UV-B光谱区域的光子能量很高，其波长与许多重要细胞成分（例如DNA）的吸收光谱重叠，臭氧消耗导致的这种增强的UV-B辐射对暴露在太阳辐射下的任何生物都构成重大威胁。在本提案中，我们关注的是太阳紫外线对北极海洋浮游植物的影响，这些浮游植物构成了海洋生态系统中整个食物网的基础。该项目将以挪威特罗姆瑟大学的海洋生物站为基地，该站位于北纬70度左右，因此代表了高纬度的北极环境，但也将包括在罗弗敦群岛和靠近巴伦支海北部冰缘的船上研究。所有实验工作将使用天然浮游植物组合或北极食物网中生态相关物种的单藻浮游植物培养物。将使用原位孵育和带适当滤光片的温控孵育器来确定增强的UV-B辐射（当柱臭氧值较低时）、“正常”UV-B辐射和UV-A辐射（320-400 nm）对细胞遗传物质（DNA）的结构损伤、初级生产的损失以及浮游植物组合物种组成可能发生的变化的影响。辅助数据将包括紫外线诱导的细胞损伤程度与细胞所受紫外线的影响和总剂量之间的关系。具体的实验还将确定紫外线诱导的细胞损伤是否及时可逆，以及细胞通过合成紫外线屏蔽化合物来减轻太阳紫外线的不利影响的程度。这些研究将通过同步测量相关环境因子来支持，包括随水柱深度的入射光谱UVR和可见太阳辐射，以及上层水柱的稳定性。这些研究将与特罗姆瑟大学的人员合作进行，特罗姆瑟大学也从事挪威北部入射太阳紫外线辐射的长期监测工作。来自美国和挪威的学生将积极参与实地工作和数据分析。该合作项目的研究结果将为进一步了解增强太阳紫外线辐射对天然浮游植物的区系组成和初级生产速率的影响提供良好的数据基础。这些数据将成为未来建模工作的重要输入，以估计北极上空大气臭氧逐渐耗竭对高营养层可利用食物资源的影响。由于重要的渔业资源遍布整个北极地区，这种知识在经济和社会问题方面也很重要。

9907692Holm-HansenRecent data shows that ozone concentrations in the stratosphere over the Northern Hemisphere during the spring period (March-May) are decreasing each succeeding year, continuing the decline that has been documented during the past decade. The magnitude of the depletion in atmospheric ozone is maximal at the higher latitudes in the Arctic, with progressively less depletion at lower latitudes. Depletion of this protective layer of ozone results in enhancing UV-B radiation (280-320 nm), with the influence of these shorter UV wavelengths incident upon the earth increasing exponentially with progressive loss of ozone. As the photons in the UV-B spectral region are highly energetic and their wavelengths overlap the absorption spectrum of many important cellular components (e.g., DNA), this enhanced UV-B radiation resulting from ozone depletion represents a significant threat to any living organism which is exposed to solar radiation. In this proposal we are concerned with the impact of solar UVR on Arctic marine phytoplankton, which constitute the base of the entire food web in the marine ecosystem.The project will be based at the Marine Biological Station of the University of Tromso, Norway, which is located at approximately 70 N and hence represents a high-latitude Arctic environment, but will also include ship-board studies in the Lofoten Islands and close to the ice edge in the northern Barents Sea. All experimental work will use either natural phytoplankton assemblages or unialgal phytoplankton cultures of ecologically relevant species in the Arctic food web. Both in situ incubations and temperature-controlled incubators with appropriate optical filters will be used to determine the impact of enhanced UV-B radiation (when column ozone values are low), 'normal' UV-B radiation, and UV-A radiation (320-400 nm) on structural damage to the genetic material in cells (DNA), on the loss of primary production, and on possible changes in species composition of the phytoplankton assemblages. Ancillary data will include the relationship between the magnitude of UV-induced cellular damage and the influence and total dose of UVR experienced by cells. Specific experiments will also determine whether or not the UV-induced cellular damage is reversible in time, and also the extent to which cells can mitigate the adverse effects of solar UVR by synthesis of UV-screening compounds. These studies will be supported by simultaneous measurements of relevant environmental factors, including incident spectral UVR and visible solar radiation with depth in the water column, and stability of the upper water column.The studies will be done in cooperation with personnel from the University of Tromso, who are also engaged in long-term monitoring of incident solar UVR in northern Norway. Students from both the USA and Norway will be active participants in the field work and in analysis of the data. The results from this cooperative project should provide a good data base to better our understanding of the possible impact of enhanced solar UVR on the floristic composition of the natural phytoplankton assemblages as well as on the rate of primary production. Such data will be important inputs to future modeling efforts to estimate the impact of progressive depletion of atmospheric ozone over the Arctic on the food resources available to higher trophic levels. As important fishery resources are located throughout the Arctic regions, such knowledge is also of importance in regard to economic and societal concerns.